OF CIRCULATION, BLOOD AXI> DUCTLESS GLANDS.
SECTION A. — HEAXT AND AriTEini:?.
Pericardium. — The pericardia?!: consist? of ribrou? and serous parts. The former is adherent to the central tendon of the diaphragm below, and is lost on the great vessels above. The serous part is disposed as in Man.
Heart. — In all the Apes the heart is small, but it is slightly longer relatively to the length of the body 5n the
Gorilla than in Man. It has the same form in the adult as in Man, but Deniker »,44^ points out that it is more globular in the foetal Gibbon. Its long axis is directed downwards and to the left. The apex, which is formed by the left ventricle, lies in the fifth interspace as in Man and in the Chimpanzee. The structure of the interior of the heart does not differ in an}* important respect from that in Man. The long axis is more horizontal than in the lower Primates.
Aorta. — The aorta is divisible into the same parts as in Man, and the relations of each are similar. The branches, however, differ in many respects.
The branches of the aortic arch are arranged in one of two ways. In the first type, which is seen in all Gorillas and some Chimpanzees, the arrangement' is as in Man. In the second type (fig. 41), which occurs in